MADRID — The new system for allocating donor lungs to transplant recipients—the lung allocation score—has a built-in bias against patients with pulmonary arterial hypertension.
But the United Network for Organ Sharing, which began applying the lung allocation score to donor lungs in the United States in May 2005, is aware of the bias and plans to fix it, Dr. Stuart C. Sweet said at the annual meeting of the International Society for Heart and Lung Transplantation.
The problem arose because relatively few patients who seek lung transplants have pulmonary arterial hypertension (PAH), which meant that limited data were available to create an accurate formula for estimating a patient's likely benefit from a lung transplant, said Dr. Sweet, medical director of the pediatric lung transplant program at Washington University in St. Louis.
The lung allocation score ranks patients on the waiting list for donor lungs based on their estimated survival benefit from transplantation, which is calculated based on patients' expected survival while awaiting a transplant and their projected survival after transplantation occurs.
Another factor that has worked against PAH patients is their high mortality during the first 30 days following lung transplantation. “Among all of the diagnostic groups that get lung transplants, patients with PAH have low survival, mostly because of their high postoperative mortality,” said Dr. Reda E. Girgis, of the division of pulmonary and critical care medicine at Johns Hopkins University in Baltimore.
Dr. Girgis is leading an effort by the International Society for Heart and Lung Transplantation, and he is also working with PAH-patient support groups to get the lung allocation score changed to better reflect the needs of patients with PAH.
A relatively small number of patients who are awaiting lung transplantation have PAH. From May 4, 2005 (when the new allocation scoring system began) through Dec. 31, 2005, 2% of all lung transplants in the United States were in patients with primary pulmonary hypertension, said Dr. Denis Hadjiliadis of the lung transplantation program at the University of Pennsylvania in Philadelphia.